This program is concerned with several phases of the general problems related to the renin-angiotensin-aldosterone system and sodium metabolism in congestive heart failure, hypertension, and pregnancy. The specific areas include: 1) pathogenic mechanisms in experimental hypertension, 2) the control of renin secretion, 3) mechanisms regulating sodium excretion during pregnancy, 4) the control of aldosterone secretion and 5) the physiology of left heart failure. The methods include 1) experimental surgical procedures for production of right heart failure, left heart failure, renal hypertension and thoracic inferior vena cava constriction with ascites, and 2) chemical and bioassay methods for adrenal steroids and renin. Renin is quantified by rat bioassay and radioimmunoassay of angiotensin I. Aldosterone, corticosterone, cortisol and desoxycorticosterone are measured by the double isotope derivative assay. Electrolytes and kidney function are studied by classical methods including flame photometry, renal clearances of Cr and PAH and electromagnetic flowmeters. Cardiac output will be measured by dye dilution and aortic flow with a flowmeter.